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Lizard evolution highlights power of climate change

Tiliqua rugosa, more commonly known as the Sleepy Lizard, or Shingleback Lizard. Photo: Mike Gardner

The fragmentation of lizard habitat across Australia brought about by Ice Age aridification millions of years ago could lead to smaller current populations having a reduced ability to cope with continued climate change.

Flinders University research into populations of the Australian scincid lizard, Tiliqua rugosa (commonly known as the Sleepy Lizard, or Shingleback Lizard) has identified a prehistoric case study that shows climate change had a significant effect on genetic differences in this native animal species.

Molecular clock analyses suggest that the diversification of Australia’s lizard populations occurred in the Plio-Pleistocene epoch, which began about 5 million years ago.

Before this last glacial maximum, the Tiliqua rugosa species and others were likely to be found in multiple suitable areas across Australia rather than all retreating to a single suitable region.

However, the creation of geographic barriers –the Nullarbor region and the presence of a vast historic lake (Bungunnia) – resulted in large genetic differences occurring between lizard populations that became isolated on either side of the Nullarbor Plain, and either side of the Murray River.

Continued habitat fragmentation across Australia provides a significant threat to current lizard populations, because ensuring adequate geneflow among the species requires their free movement beyond existing geographic barriers.

“Solving this problem can be facilitated by establishing vegetation corridors between the different regions, which would help to ensure the mobility and conservation of these populations,” says Flinders University molecular ecologist Associate Professor Mike Gardner.

“This problem represents a bigger picture about what is happening to species, and underlines that species survival depends on ensuring the maintenance of long-term genetic diversity.

“It highlights that we have seen such dramatic change to the landscape – and it continues to change at an accelerating pace. Species simply can’t have the same levels of genetic diversity that they had in the past.”

Associate Professor Mike Gardner – continuing the lizard legacy left by the late Professor Michael Bull.

Herpetologist Associate Professor Gardner says Flinders’ continuing research into the genetics of Australian lizard populations illustrates the heightened need for animal refuge habitats to protect the future of existing species.

“It’s vitally important to maintain historical refuge areas, which must become a priority of land managers,” he says.

Work continues in the longest-running lizard research in the Southern Hemisphere. With costs around $50,000 each year, for field work and other expenses, the Flinders University scientists rely on the generous support of the community who can give to the dedicated alumni appeal.